1. Field of the Invention
This invention relates to a spread illuminating apparatus for illuminating a front portion of a display and various kinds of reflection type of displays and so on, in particular for an illuminating means for a liquid crystal display.
2. Conventional Art
A liquid crystal display which functions at a low energy consumption has features such as thin in size and light in weight, so that the demand as an indication apparatus primarily for computer has been increased. However, since the liquid crystal itself does not emit a light, for viewing an image, it needs an illuminating means for observing images, different from a light-emitting element, such as a picture tube.
In particular, in the midst of recent tendency for requiring a thinner type of appliance, as an illuminating means for a liquid crystal display, a spread illuminating apparatus of a thin plate-like type of side light system (light conductive plate system) has been utilized.
Hereinafter, a constitution of a side light system of the spread illuminating apparatus 41 is explained based on FIG. 13.
Reference numeral 42 shows a bar-like light source lamp such as cold cathode fluorescent lamp (CCFL) or hot cathode fluorescent lamp (HCFL) to be used as a light source for a spread illuminating apparatus. A transparent substrate 43 made of a material having a high transparency is configured of a thin rectangular in section, and along with one side end 44, a light source lamps 42 is disposed at a given spacing. Now, the transparent substrate 43 may be formed wedge-like, wherein, in order to reduce the weight, in such a manner as the transparent substrate 43 is made the thinner, the farther from the side end 44 at which the light source lamp 42 is located.
Around the light source lamp 42 and at the position where the side end 44 does not face, a lamp reflector 45 formed by vaporizing the silver etc. on a film is disposed. By providing thus the lamp reflector 45, most light emitted from the light source lamp 42 is enabled to make an incidence into the transparent substrate 43 from the side end 44. Further, in order to prevent the light from being leaked, to the side ends other than the side end 44 of the transparent substrate 43 (in FIG. 13, merely one side end 46 which opposes to the one side end 44 is indicated) reflection members 47 made of reflection tapes and so on are applied.
On a rear surface 48 (low in FIG. 13) of the transparent substrate 43, without depending on the distance from the light source lamp 42, in order to make the screen of the spread illuminating apparatus emitted evenly, a light diffusion pattern 49 (later being explained in details) is formed, and further downward a reflection plate 50 is disposed in such a manner it covers all of the rear surface 48. The reflection plate 50 makes the light which tries to emit from the rear surface 48 of the transparent substrate 43 reflected and directed toward the front surface 51 (upper in FIG. 13) of the transparent substrate 43.
Further, a spread illuminating apparatus 41 is provided with a diffusion plate 52 in such a manner as it covers whole of the front surface 51 of the transparent substrate 43. The reason why this diffusion plate 51 is disposed is explained. That is, since most light which progresses in the transparent substrate 43 and emits from the surface 51 are observed in such a manner as merely the light diffusion pattern 49 brightens (so called a dot-image), in order to remove such dot-image the light diffusion plate 52 makes the light progressing therein overlapped (that is, diffused) and emitted the light approximately evenly on the transparent substrate 43 by making the density and distribution of the emitting light even. The light diffusion pattern 49 shown in FIG. 14, as disclosed in the patent laid-open publication No. Hei 5-134251, is formed in such a manner as the diameters of the dots disposed thereon become gradually large in proportion to approaching the side end 46 opposing to the side end 44, along which the light source lamp 42 is disposed. The light diffusion pattern 49 is formed by coating a medium containing light diffusing and reflecting materials directly on the rear surface 48 of the transparent substrate 43 by a screen printing process.
Thus, the light diffusion pattern 49 is formed by changing the ratio in which, depending on its position per unit area, the medium containing the light diffusing and reflecting materials are defined, (hereinafter referred the ratio by which a given material may occupy per unit to as xe2x80x9carea densityxe2x80x9d), so that the light volume to be emitted from the surface 51 is changed by being reflected by the light diffusion pattern 49. That is, since the brightness of the light becomes the higher the closer to the light source lamp 42, in order to realize an even spread emitting, the area density of the light diffusion pattern 49 is formed in such a manner as it becomes the large the far from the light source lamp 42. Thereby, since the light volume to be reflected on the surface 51 separated as far from the light source lamp 42, the balance between the distance from the light source lamp 42 and the light volume to be reflected by the light diffusion pattern 49 is to be considered to make the whole body emitted even. Here, although the light diffusion pattern 49 are, in FIG. 14, not sectional, hatching is applied for an easy looking.
Although the light diffusion pattern 49 is adapted to be formed by coating the medium containing the light diffusion and reflecting materials on the rear surface 48 of the transparent substrate 43, it is not limited to such a construction but may be constructed by what is to increase the light reflection, for instance, as disclosed in Japanese Patent Laid-open Publication No. Hei 9-33923, a finely formed concavo-convex surface may be directly formed on the rear surface 48 of the transparent substrate 43 and is adapted to make the light diffused and reflected.
Further, as an illuminating means for a liquid crystal display apparatus, in particular, for what is used as an auxiliary means for a reflection type of a liquid crystal display apparatus, a different type of illuminating apparatus other than the above spread illuminating apparatus 41 is explained as follows. The reflection type of a liquid crystal display is a type which can illuminate the screen making use of environmental light as an illuminating light and there is no need of an internal illuminating means, but when the surrounding is dark, since it becomes difficult to observe the screen, an auxiliary illuminating means will be necessary. As a preferable example, of such auxiliary illuminating means for a liquid crystal display, in the patent application No. Hei 9-347648, a spread illuminating apparatus for being disposed in front of (on both of) a reflection type of a liquid crystal display is disclosed.
What is shown in this type of an illuminating apparatus 1xe2x80x2 in FIG. 15, is what is used while covering an observation surface F of a liquid crystal display element L of the above constitution and its constitution resides, as shown in FIGS. 15 and 16, in that a bar-like light source lamp 4 is disposed close to one side end 3 of a plate-like transparent substrate 2 having a high transparency and formed rectangular in section. The light source lamp 4 is formed with a cold cathode fluorescent lamp (CCFL) or a hot cathode fluorescent lamp (HCFL). In addition, as the transparent substrate 2, so as to reduce the weight, what becomes gradually thinner in thickness as it separates far from the one side end 3 wedgewise, is used.
Here, one side of the transparent substrate 2 (lower in FIG. 16) which abuts to a reflection type of the liquid crystal element L in FIG. 15 is to be called as a lower surface 5 and another side(upper in FIG. 16) which is an observation surface (picture surface) opposite to one side is to be called as an upper surface 6 (front surface).
On the upper surface 6 of the transparent substrate 2, a light reflection pattern 7 is constituted with a plurality of groove portions 8 of the transparent substrate 2 approximately triangular in section and plane portions 9 adjacent to the groove portions 8. The light reflection pattern 7 is formed in spacing thereof differently in such a manner as the brightness of the transparent substrate 2 becomes even at which position from the light source lamp 4 the groove 8 is located. That is, the ratio of the width (occupation area)of the groove 8 to the width (occupation area) of the plane portion 9 is settled so as to become gradually larger in proportion to the distance of the groove 8 separating from one side end 3 of the transparent substrate 2. For reference, since the groove 8 of the light reflection pattern 7 is quite minute, those may not be recognized by observing the picture surface by naked eyes.
When such a spread illuminating apparatus 1xe2x80x2 as an auxiliary illumination is added to a reflection type of the liquid crystal display element L, the light emitted from the light source lamp 4 enters the transparent substrate 2 from the one side end 3 thereof and while repeating reflection and refraction during progressing inside thereof and toward the opposite surface 10, the light emits little by little from the lower surface 5 which illuminates the reflection type of the liquid crystal element L disposed close to the transparent substrate 2.
Further, since the transparent substrate 2 is provided with the light reflection pattern 7, the light emitted from the lower surface 5 can be made to be distributed even.
For reference, although an illustration in FIGS. 15 and 16 is omitted, since the portions around the light source lamp 4 and the one side end 3 are covered with a film-like reflecting member, a coupling efficiency of the light may be increased. Further, since by covering the side ends of the transparent substrate 2 other than the side end 3 are covered with the reflecting member, the light is prevented from emitting from the side ends, the volume of illuminating light emitted therefrom is large comparing with the other surfaces, it is preferable to cover them with the reflecting members.
Further, since the reflection angle of the light is changed according to the shape of the groove portions 8 of the light reflection pattern 7, the emitting direction of the light from the lower surface 5 of the transparent substrate 2, in order to make the light emitted mostly in the direction perpendicular to the lower surface 5 (i.e. in the front direction), the shape of the groove portion 8 can be suitably settled.
Now, as an illuminating means for a liquid crystal display apparatus (including a reflection type of a liquid crystal display element L), each of spread illuminating apparatus 41,1xe2x80x2 uses, as a light source, a cold cathode fluorescent lamp (CCFL) or a hot cathode fluorescent lamp (HCFL), so that there are following problems.
That is, in response to the recent request for a need in which a device is made to become thinner the above fluorescent lamps to be used as a light source lamp 4, 42 has to have a tendency in which its diameter is formed to be outstandingly small, in accordance with which such a device is apt to be damaged by a small shock to need a special handling for that.
In addition, in order to make the fluorescent lamps to be used as the light source lamps 4, 42 emitted, in general, a high voltage more than several hundreds to 1000 V is needed, and for that purpose, the fluorescent lamps are provided with a complicated switching on circuit so-called an inverter. Accordingly, a space for accommodating such an inverter has to be secured, on the other hand, in the demand for requiring for making a device thinner and miniaturized, a demand that the space for an inverter is required to be as small as possible has been increased. Also, there is a problem that for protection against the high voltage a complicated countermeasure has to be taken.
Although it is possible to solve the above problem, in place of such fluorescent lamps (bar-like light source) as the light source lamp 4, 42, by using a spot-like light source for instance such as a light bulb or an emitting diode, if merely disposing such a spot-like light source at the position where the light source lamp 4, 42 of the conventional spread illuminating apparatus 41, 1xe2x80x2, there can be a problem that only the area closer to the spot-like light source is illuminated and a spread and even emitting is not realized.
Accordingly, the present invention is to provide a spread illuminating apparatus, which is improved in an easy handling by preventing it from being broken due to an increase of a shock resistance and which can generate an evenly spread light emitting by using a light source lamp which can avoid a consideration for safety such as a switching apparatus like an inverter by switching on at low voltage.
According to a first aspect of the invention, in a side light system of the spread type of illuminating apparatus which comprises a bar-like light source disposed nearby a side of a transparent substrate, said light source consists of a bar-like light conductive member made of a transparent material and disposed close to at least one side end of the transparent substrate, a spot-like light source disposed on one of the bar-like light conductive member and a light reflection plate disposed on the other end of the light conductive member.
According to this aspect, by disposing the spot-like light source on one end of the light conductive member disposed close to the side end of the transparent substrate, the light emitted from the spot-like light source enters the light conductive member, is discharged from the opposing surface to the transparent substrate and such discharged light enters the transparent substrate. Further, the light reached the other end of the light conductive member is reflected by the reflection plate, again enters light conductive member and progresses therein toward the spot-light source. This reflected light too is emitted from the surface of the light conductive member opposing to the transparent substrate and enters the transparent substrate. Therefore, the light emitting efficiency can be increased.
According to a second aspect of the spread illuminating apparatus of the present invention, a manner of reflection of the reflection plate is determined in consideration of a reflection manner of an optical path conversion means provided on at least one of the surface of the light conductive member opposing to the transparent substrate or opposite to that surface.
The emitting light entered the light conductive member from the spot-like light source is reflected or refracted due to the optical path conversion means and emitted from the surface opposing to the one surface of the transparent substrate. Therefore, by considering the manner, for instance, a relation between the distance from the spot-like light and a light amount and determining the manner of reflection of the reflection means (plate), a brightness of all over the light conductive member can be appropriately controlled.
According to a third aspect of the spread illuminating apparatus a reflection plate disposed adjacent to the other end of the light conductive member is used. And by this reflection plate, the-emitted light reached the other end of the light conductive member is made to be reflected and progressed again toward the spot-like light source. This reflected light too is made to be emitted from the surface of the light conductive member and enters the transparent substrate. Therefore, the light emitting efficiency of the light conductive member can be increased.
Further, In a spread illuminating apparatus according to a fourth aspect of the present invention, the reflection means is formed from a metal vaporized layer on the other end of the light conductive member. And, by the metallic layer, the emitting light reached the other end of the light conductive member is reflected, again it is made to progress in the light conductive member toward the spot-like light source . This reflected light too is emitted from surface opposing to the transparent substrate and enters the transparent substrate. Therefore, the light emitting efficiency of the light conductive member can be increased.
Further, in a spread illuminating apparatus according to a fifth aspect of the present invention, said light reflection means is a coating layer applied on the other end of the light conductive member. And, by the coating layer the emitted light reached the other end of the light conductive member is made reflected, and again progresses toward the spot-like light source. This reflected light too is emitted from the surface of the light conductive member opposing to the transparent substrate. Therefore, the light emitting efficiency of the light conductive member can be increased.